// Copyright 2014 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef UI_ANDROID_EDGE_EFFECT_BASE_H_
#define UI_ANDROID_EDGE_EFFECT_BASE_H_

#include "base/time/time.h"
#include "ui/gfx/geometry/size_f.h"
#include "ui/gfx/transform.h"

namespace cc {
class Layer;
}

namespace ui {

// A base class for overscroll-related Android effects.
class EdgeEffectBase {
public:
    enum State {
        STATE_IDLE = 0,
        STATE_PULL,
        STATE_ABSORB,
        STATE_RECEDE,
        STATE_PULL_DECAY
    };

    enum Edge { EDGE_TOP,
        EDGE_LEFT,
        EDGE_BOTTOM,
        EDGE_RIGHT,
        EDGE_COUNT };

    virtual ~EdgeEffectBase() { }

    virtual void Pull(base::TimeTicks current_time,
        float delta_distance,
        float displacement)
        = 0;
    virtual void Absorb(base::TimeTicks current_time, float velocity) = 0;
    virtual bool Update(base::TimeTicks current_time) = 0;
    virtual void Release(base::TimeTicks current_time) = 0;

    virtual void Finish() = 0;
    virtual bool IsFinished() const = 0;
    virtual float GetAlpha() const = 0;

    virtual void ApplyToLayers(Edge edge,
        const gfx::SizeF& viewport_size,
        float offset)
        = 0;
    virtual void SetParent(cc::Layer* parent) = 0;

protected:
    // Computes the transform for an edge effect given the |edge|, |viewport_size|
    // and edge |offset|. This assumes the the effect transform anchor is at the
    // centered edge of the effect.
    static gfx::Transform ComputeTransform(Edge edge,
        const gfx::SizeF& viewport_size,
        float offset);

    // Computes the maximum effect size relative to the screen |edge|. For
    // top/bottom edges, thsi is simply |viewport_size|, while for left/right
    // edges this is |viewport_size| with coordinates swapped.
    static gfx::SizeF ComputeOrientedSize(Edge edge,
        const gfx::SizeF& viewport_size);
};

} // namespace ui

#endif // UI_ANDROID_EDGE_EFFECT_BASE_H_
